1. Field of the Invention
The present invention relates to a profile processing method for processing a concave or a convex profile to a work using a rotary tool and a processing machine therefor. For example, the present invention relates to a profile processing method for processing a predetermined concave or convex profile onto a mold material using an end mill and a processing machine therefor.
2. Description of Related Art
Conventionally, when a concave portion, an annular groove for example, is carved onto a work using a rotary tool such as an end mill, the innermost part of the annular groove is first carved and other part is further carved by moving the end mill gradually from inside to outside.
For instance, when an annular groove 101 shown in FIGS. 7(A) and 7(B) carved, the end mill EM is initially moved along the inner side of the annular groove 101 for carving. Consequently, the end mill EM is moved outwardly in a width direction of the annular groove 101 at a predetermined amount, and the annular groove 101 is further carved from the position by moving the end mill EM along the annular groove 101. Accordingly, the profile is carved by moving the end mill EM gradually outwardly and repeating similar movement.
[Problem in Cutting Condition]
However, according to the conventional carving method, an up-cut (cutting upwardly) and a down-cut (cutting downwardly) exist in a work together. More specifically, in FIG. 7, the annular groove 101 is down-cut (cutting downwardly) relative to the inner surface of the annular groove 101 when the end mill EM is moved along the inner side of the annular groove 101, however, the annular groove 101 is up-cut (cutting upwardly) when the outer side is carved. Therefore, it is difficult to obtain good finish surface accuracy in all of carved surfaces, and the life span of the tool is shortened.
Generally speaking, since a swarf thickness in conducting the up-cut (cutting upwardly) starts from zero and increases gradually as shown in FIG. 8(A), it is not possible to cut when the swarf thickness is zero because of the absence of the room for an edge to be cut into the work. Accordingly, the edge rubs a surface carved by the previous edge when the work is started to be up-cut.
On the other hand, since a swarf thickness in conducting the down-cut (cutting downwardly) is the greatest at the beginning of cutting and is decreased gradually, a force for separating the edge from the work is generated when the swarf thickness is zero.
Therefore, the up-cutting (cutting upwardly) is shorter in tool's life and is more likely to cause grinding burn than the down-cut (cutting downwardly). So, when the up-cut (cutting upwardly) and the down-cut (cutting downwardly) coexist in a work as in a conventional carving method, it is difficult to obtain good finish surface accuracy in all of the carving surfaces and the tool's life is shortened.
[Problem in Moving Direction]
Further, since the end mill EM is always moved from inside toward outside for carving concave portion in a conventional method, a contact area of the end mill EM relative to the work is widened as the end mill EM is moved outwardly thereby increasing the load applied on the tool. Therefore, the tool's life is further shortened.
[Object]
The object of the present invention is to solve aforesaid problems, that is, to provide a profile processing method and processing machine therefor which can obtain a good finish surface accuracy in all the carving surfaces and curb the decrease in tool's life.